This chapter is from the book

This chapter covers the following subtopics from the Cisco CCIE Routing and Switching written exam blueprint. Refer to the full blueprint in Table I-1 in the Introduction for more details on the topics covered in each chapter and their context within the blueprint.

Modular QoS CLI (MQC)

Network-Based Application Recognition (NBAR)

QoS Classification

QoS Marking

Cisco AutoQoS

The goal of classification and marking tools is to simplify the classification process of other quality of service (QoS) tools by performing complicated classification steps as few times as possible. For example, a classification and marking tool might examine the source IP address of packets, incoming Class of Service (CoS) settings, and possibly TCP or UDP port numbers. Packets matching all those fields might have their IP Precedence (IPP) or DiffServ Code Points (DSCP) field marked with a particular value. Later, other QoS tools—on the same router/switch or a different one—can simply look for the marked field when making a QoS decision, rather than having to perform the detailed classification again before taking the desired QoS action.

“Do I Know This Already?” Quiz

Table 3-1 outlines the major headings in this chapter and the corresponding “Do I Know This Already?” quiz questions.

To best use this pre-chapter assessment, remember to score yourself strictly. You can find the answers in Appendix A, “Answers to the ‘Do I Know This Already?’ Quizzes.”

According to the DiffServ RFCs, which PHB defines a set of three DSCPs in each service class, with different drop characteristics for each of the three DSCP values?

Expedited Forwarding

Class Selector

Assured Forwarding

Multi-class-multi-drop

Which of the following are true about the location of DSCP in the IP header?

High-order 6 bits of ToS byte/DS field.

Low-order 6 bits of ToS byte.

Middle 6 bits of ToS byte.

Its first 3 bits overlap with IP Precedence.

Its last 3 bits overlap with IP Precedence

Imagine that a packet is marked with DSCP CS3. Later, a QoS tool classifies the packet. Which of the following classification criteria would match the packet, assuming that the marking had not been changed from the original CS3 marking?

Match on DSCP CS3

Match on precedence 3

Match on DSCP AF32

Match on DSCP AF31

Match on DSCP decimal 24

Imagine that a packet is marked with AF31. Later, a QoS tool classifies the packet. Which of the following classification criteria would match the packet, assuming that the marking had not been changed from the original AF31 marking?

Match on DSCP CS3

Match on precedence 3

Match on DSCP 24

Match on DSCP 26

Match on DSCP 28

Examine the following output from a router that shows a user adding configuration to a router. Which of the following statements is true about the configuration?

Examine the following example of commands typed in configuration mode to create a class map. Assuming that the class fred command was used inside a policy map, and the policy map was enabled on an interface, which of the following would be true with regard to packets classified by the class map?